Breast cancer is a cancer which develops in breast tissues, and a therapeutic means for healing breast cancer is, in principle, surgery. In addition, chemotherapy or radiotherapy is used in combination with such surgery. In recent years, the number of incidences of breast cancer has rapidly increased, and breast cancer has occupied first place in morbidity among female cancers in Japan.
The highest risk factor of developing breast cancer is family history. In addition, it is considered that a long-term state of estrogen excess is reflected in the development of breast cancer. Specifically, there have been known risk factors such as no pregnancy history/parity, no experience of breast feeding after the birth of the first child, an early age at menarche, a late age at menopause, and experience of hormone therapy.
It has been reported that soy isoflavones have female hormone-like action and inhibitory action on carcinogenesis (Non Patent Documents 1-3 and Patent Document 1). On the other hand, it has been known that a group of lactic acid bacteria of the genus Streptococcus, the genus Bifidobacterium, the genus Lactobacillus, and the like have inhibitory action on recurrence of bladder cancer, arginine deiminase activity, and the like (Patent Documents 2 and 3). Moreover, it has also been known that dead cells of microorganisms of the genus Lactobacillus have anticarcinogenic action (Patent Document 4).